Ultrafine dry powder fire extinguishing device in elevated warehouses

Ultra-fine dry powder fire extinguishing agent, the smaller the particle size, the higher the fire extinguishing performance. Currently, there are two main types of ABC ultrafine dry powder fire extinguishing agents used in the market:

• ammonium phosphate.
• ultrafine dry powder fire extinguishing agent.

Ammonium Phosphate

For this type, its main extinguishing mechanism is to block the combustion chain reaction, which is the chemical inhibition effect. 90% of the particle size of this fire extinguishing agent is below 20UM, Its fire extinguishing efficiency is ≤0.120/m3, which is 4 times that of ordinary dry powder fire extinguishing agent.

Ultrafine ABC Dry Chemical Powder Fire Extinguishing Agent

For this type, 90% of the particle size of the fire extinguishing agent is below 15UM, This type of fire extinguishing agent organically combines the advantages of chemical fire extinguishing with the advantages of physical fire extinguishing through a composite method. The chemical suppression effect on flame burning, the suffocation effect on flameless combustion, and the isolation and cooling effect on thermal radiation are the concentrated manifestations of this type of fire extinguishing agent.

Better Option – Ultrafine ABC Dry Chemical Powder

When extinguishing a solid material fire, the composite material particles of the fire extinguishing agent form a glassy film on the surface of the burning solid at high temperatures, isolating the combustion material from the air and instantly extinguishing the flameless combustion of the solid. The effectiveness of this type of fire extinguishing agent is ≤ 0.065kg/m3, which is more than 10 times that of ordinary ABC dry powder fire extinguishing agents.

Due to the dense stacking of goods in elevated warehouses, when a fire occurs, the fire spreads quickly; To quickly extinguish the fire and reduce the losses caused by the fire, people should choose fire extinguishing agents with high fire extinguishing efficiency. At the same time, it can effectively reduce the number of fire extinguishing devices hanging on elevated shelves and reduce the damage caused by elevated shelves.

DESIGN OF FIRE EXTINGUISHING SYSTEM

There are generally three ways to design a dry powder fire extinguishing system:

• Total flooding fire extinguishing application.
• Local protection fire extinguishing application.

Design of Total Flooding Fire Extinguishing Application

The total flooding application fire extinguishing system refers to the specified time to spray a certain concentration of ultrafine dry chemical fire extinguishing agent into the protective area. and make it an evenly filled fire extinguishing system for the entire protective zone.

The elevated warehouse is high and has a large volume, the height of this warehouse is usually 8 to 28 meters, volume exceeding 20000 cubic meters; It is difficult to achieve the same level of extinguishing concentration as the extinguishing agent sprayed in such a tall space within the specified extinguishing time.

At the same time, the logistics method of automated warehouse access cannot separate the warehouse into the required space for total flooding.

Therefore, it is not appropriate to use the total flooding application of the fire extinguishing system for elevated warehouses.

Design of Local Protection Fire Extinguishing Application

The local protection application fire extinguishing system is a fire extinguishing system that directly sprays dry powder extinguishing agents toward the protected object or areas considered dangerous.

Article 3.3.1 of GB50347 “Code for Design of Dry Powder Fire Extinguishing Systems” stipulates that “the design of local application fire extinguishing systems can use either the area method or the volume method.

When the fire location of the protected object is a plane, the area method should be used; when the area method cannot completely cover all surfaces, the volume method should be used”.

A. Area Method Design

According to the standard, since the protection area of the nozzle (or nozzle) of the fire extinguishing device is determined by the vertical direction of the protected surface, the calculation of the protection area also needs to take the area of the vertical projection of the overall protection surface.

When multiple fire extinguishing devices are used, the edges of their projected areas should overlap each other to ensure that the projected area can fully cover the protected object and leave no gaps in its coverage.

The area method applies to fire extinguishing systems for Class B (liquid) fires and other flat-protected objects. Because the goods in the dense shelves in the elevated warehouse, and even the entire dense shelves, are three-dimensional, not only the top plane of the goods needs to be protected, but also the four sides and bottom, and these goods are multi-level and dense, which cannot be covered by the vertical projection area.

Therefore, we cannot use the area method for the design of fire suppression systems in elevated warehouses.

B. Volume Method Design

Due to the need to extinguish the flat fire on the top of the goods in the dense shelves of the elevated warehouse, as well as the fires on the four sides and the bottom, the volume method should be used in the design of the fire extinguishing system.

According to relevant domestic and foreign standards, the volume of the protected object should be calculated using the assumed volume of the enclosed cover, with the bottom of the enclosed cover being the actual bottom. When there is no actual fence structure on the sides and top of the enclosed cover, The distance from them to the outer edge of the protected object is required to be no less than 1.5 meters.

The area method and volume method are two different design methods for local protection fire extinguishing systems. The area method design applies to designs that protect objects that are flat, such as surface protection for limited flammable liquids. The volumetric design method applies to designs that protect objects that are polyhedral, such as goods that exhibit three-dimensional properties items, shelves, etc. The two methods apply different protection objects, such as the designed dosage of extinguishing agent and extinguishing. The requirements for the arrangement of fire devices also vary.

C. Area Method Design VS Volume Method Design

If the area method is used for the design of the ultra-fine dry powder fire extinguishing system in an elevated warehouse, it will inevitably result in a serious shortage of the designed amount of fire extinguishing agent and the number of fire extinguishing devices, which will not meet the requirements of the fire extinguishing concentration and prevent the fire that should have been extinguished from being extinguished.

When arranging the fire extinguishing devices, it will also prevent the protection of several surfaces other than the vertical plane, and prevent these fires from being extinguished.

We should use the volume method to design the dry powder fire extinguishing systems in elevated warehouses. Only in this way can we ensure that in the event of a fire, the extinguishing agent sprayed will extinguish the fire in all directions, playing a role in protecting personal and property safety.

CONCLUSION

In summary, the elevated warehouse has a large space. Due to the dense placement of objects and other characteristics, when selecting ultrafine dry powder fire extinguishing devices for fire protection facilities, it is advisable to choose fire extinguishing devices with good spraying performance.

The fire extinguishing agent filled in the fire extinguishing device should use ultrafine dry powder fire extinguishing agents with high fire extinguishing efficiency.

We should use the volumetric method to design fire-extinguishing devices